Dehydrogenation with a catalytic composite containing platinum,rhenium and tin

ABSTRACT

DEHYDROGENATABLE HYDROCARBONS ARE DEHYDROGENATED BY CONTACTING THEM AT DEHYDROGENATION CONDITIONS WITH A CATALYTIC COMPOSITE COMPRISING A COMBINATION OF CATALYTICALLY EFFECTIVE AMOUNTS OF A PLATINUM GROUP COMPONENT, A RHENIUM COMPONENT AND A TIN COMPONENT WITH A POROUS CARRIER MATERIAL. IN A PREFERRED EMBODIMENT, THE CATALYST ALSO CONTAINS AN ALKALI OR ALKALINE EARCH COMPONENT. A SPECIFIC EXAMPLE OF THE CATALYTIC COMPOSITE USED IN THIS DEHYDROGENATION METHOD IS A COMBINATION OF A PLATINUM COMPONENT, A RHENIUM COMPONENT, A TIN COMPONENT AND AN ALKALI OR ALKALINE EARTH METAL WITH AN ALUMINA CARRIER MATERIAL.

United States Patent DEHYDROGENATION WITH A CATALYTIC COM- POSITECONTAINING PLATINUM, RHENIUM AND TIN Richard E. Rausch, Mundelein, 111.,assignor to Universal Oil Products Company, Des Plaines, Ill.

No Drawing. Original application July 9, 1969, Ser. No. 840,471. Dividedand this application June 8, 1970, Ser. No. 44,606

Int. Cl. C07c 11/02, 15/10 US. Cl. 260-669 21 Claim ABSTRACT OF THEDISCLOSURE CROSS-REFERENCES 'TO RELATED APPLICATIONS This application isa division of my application entitled Dehydrogenation Method andCatalytic Composite For Use Therein, Ser. No. 840,471, filed July 9,1969, which application is, in turn, a continuation-in-part of myapplication entitled Hydrocarbon Conversion Process and CatalystTherefor, Ser. No. 819,114, filed Apr. 24, 1969.

DISCLOSURE The subject of the present invention is, broadly, an improvedmethod for dehydrogenating a dehydrogenatable hydrocarbon to produce ahydrocarbon product containing the same number of carbon atoms but fewerhydrogen atoms. In another aspect, the present invention encompasses amethod of dehydrogenatingnormal paraffin hydrocarbons containing 4 to 30carbon atoms per molecule to the corresponding normal mono-olefin withminimum production of side products. In yet another aspect, the presentinvention relates to the use of a novel catalytic composite comprising acombination of catalytically effective amounts of a platinum groupcomponent, a rhenium component, a tin component, and an alkali oralkaline earth component with a porous carrier material, which catalyticcomposite has highly preferred characteristics of activity, selectivity,and stability when it is employed in the dehydrogenation ofdehydrogenatable hydrocarbons such as aliphatic hydrocarbons, naphthenehydrocarbons, and alkylaromatic hydrocarbons.

The conception of the present invention followed from my search for anovel catalytic composite possessing hydrogenation-dehydrogenation andcracking functions and having superior conversion, selectivity, andstability characteristics when employed in hydrocarbon conversionprocesses that have traditionally utilized dual'function catalyticcomposites. In one of my prior applications, I

disclosed a significant finding with respect to a catalytic compositemeeting these requirements. More specifically, I determined that acatalytic composite comprising a combination of a platinum groupcomponent, a rhenium component, and a tin component with a porouscarrier material has superior activity, selectivity, and stabilitycharice A acteristics when it is employed in a process which heretoforeutilized dual-function catalytic composites such as a dehydrogenationprocess. After an extensive investigation of the use of this compositein a dehydrogenation reaction, I have now ascertained that aparticularly preferred catalytic composite for dehydrogenation containsnot only a platinum group component, a rhenium component, and a tincomponent, but also an alkali or alkaline earth component.

The dehydrogenation of dehydrogenatable hydrocarbons is an importantcommercial process because of the great and expanding demand fordehydrogenated hydrocarbon for use in the manufacture of variouschemical products such as detergents, plastics, synthetic rubbers,pharmaceutical products, high octane gasoline, perfumes, drying oils,ion-exchange resins, and various other products well known to thoseskilled in the art. One example of this demand is in the manufacture ofhigh octane gasoline by using C, and C mono-olefins to alkylateisobutane. Another example of this demand is in the area ofdehydrogenation of normal paraffin hydrocarbons to produce normalmono-olefins having 4 to 30 carbon atoms per molecule. These normalmono-olefins can, in turn, be utilized in the synthesis of vast numbersof other chemical products. For example, these normal mono-olefins havebecome of substantial importance to the detergent industry where theyare utilized to alkylate an al kylatable aromatic such as benzene, withresultant transformation of the product arylalkane into a wide varietyof biodegradable detergents such as the alkylaryl sulfonate type ofdetergent which is most widely used today for household, industrial, andcommercial processes. Still another large class of detergents producedfrom these normal mono-olefins are the oxyalkylated phenol derivativesin which the alkyl phenol base is prepared by the alkylation of phenolwith these normal mono-olefins. Still another type of detergentsproduced from these normal mono-olefins are the biodegradablealkylsulfates formed by the direct sulfation of the normal mono-olefin.Likewise, the olefin can be subjected to direct sulfonation with sodiumbisulfite to make biodegradable alkylsulfonates. As a further example,these mono-olefins can be hydrated to produce alcohols which then, inturn, can be used to produce plasticizers and/or synthetic lube oils.

Regarding the use of products made by the dehydrogenation ofalkylaromatic hydrocarbons, these find wide application in industriesincluding the petroleum, petrochemical, pharmaceutical, detergent,plastic industries, and the like. For example, ethylbenzene isdehydrogenated to produce styrene which is utilized in the manufactureof polystyrene plastics, styrene-butadiene rubber, and the likeproducts. Isopropylbenzene is dehydrogenated to form alphamethyl styrenewhich, in turn, is extensively used in polymer formation and in themanufacture of drying oils, ion exchange resins, and the like material.

Responsive to this demand for these dehydrogenation products, the arthas developed a number of alternative methods to produce them incommercial quantities. One method that is widely utilized involves theselective dehydrogenation of dehydrogenatable hydrocarbon by contactingthe hydrocarbon with a suitable catalyst at dehydrogenation conditions.As is the case with most catalytic procedures, the principal measure ofeffectiveness for this dehydrogenation method involves the ability toperform its intended function with minimum interference from sidereactions for extended periods of time. The analytical terms used in theart to broadly measure how well a particular catalyst performs itsintended functions in a particular hydrocarbon conversion reaction areactivity, selectivity, and stability, and for purposes of discussionhere these terms are generally defined for a given reactant as follows:(1) activity is a measure of the catalysts ability to convert thehydrocarbon reactant into products at a specified severity level whereseverity level means the conditions used-that is, the temperature,pressure, contact time, and presence of diluents such as H (2)selectivity usually refers to the amount of desired product or productsobtained relative to the amount of the reactant converted; (3) stabilityrefers to the rate of change with time of the activity and selectivityparametersobviously the smaller rate implying the more stable catalyst.More specifically, in a dehydrogenation process, activity commonlyrefers to the amount of conversion that takes place for a givendehydrogenatable hydrocarbon at a specified severity level and istypically measured on the basis of disappearance of the dehydrogenatablehydrocarbon; selectivity is typically measured by the amount, calculatedon a mole percent of converted dehydrogenatable hydrocarbon basis, ofthe desired dehydrogenated hydrocarbon obtained at the particularseverity level; and stability is typically equated to the rate of changewith time of activity as measured by disappearance of thedehydrogenatable hydrocarbon and of selectivity as measured by theamount of desired hydrocarbon produced. Accordingly, the major problemfacing workers in the hydrocarbon dehydrogenation art is the developmentof a more active and selective catalytic composite that has goodstability characteristics.

I have now found a catalytic composite which possesses improvedactivity, selectivity, and stability when it is employed in a processfor the dehydrogenation of dehydrogenatable hydrocarbons. In particular,I have determined that a combination of catalytically effective amountsof a platinum group component, a rhenium component, and a tin componentwith a porous, refractory carrier material enables the performance of adehydrogenation process to be substantially improved. Moreover, I haveobserved particularly good results when this composite is combined withan alkali or alkaline earth component and utilized to producedehydrogenated hydrocarbons containing the same carbon structure as thereactant hydrocarbon but fewer hydrogen atoms. This last composite isparticularly useful in the dehydrogenation of long chain normalparaflins to produce the corresponding normal monoolefin withminimization of side reactions such as skeletal isomerization,aromatization and cracking.

It is, accordingly, one object of the present invention to provide anovel method for the dehydrogenation of dehydrogenatable hydrocarbonsutilizing a catalytic composite comprising a platinum group component, arhenium component, and a tin component combined with a porous carriermaterial. Another object is to provide an improved method for thedehydrogenation of normal paraflin hydrocarbons to produce normalmono-olefins which method minimizes undesirable side reactions such ascracking, skeletal isomerization and aromatization.

In brief summary, one embodiment of the present invention involves a.method for dehydrogenating a dehydrogenatable hydrocarbon whichcomprises contacting the hydrocarbon with a catalytic compositecontaining a platinum group component, a rhenium component, and a tincomponent combined with a porous carrier material at dehydrogenationconditions. The catalytic composite contains these components in amountscalculated on an elemental basis, of about 0.01 to about 1 wt. percentplatinum group metal, about 0.01 to about 1 wt. percent rhenium, andabout 0.01 to about wt. percent tin.

A second embodiment relates to the dehydrogenation method described inthe first embodiment wherein the dehydrogenatable hydrocarbon is analiphatic compound containing 2 to 30 carbon atoms per molecule.

Another embodiment relates to a method for dehydrogenating adehydrogenatable hydrocarbon which com prises contacting the hydrocarbonat dehydrogenation conditions with a catalytic composite comprising acombination of a platinum group component, a rhenium component, a tincomponent, and an alkali or alkaline earth component with an aluminacarrier material. These components are present in amounts suflicient toresult in the catalytic composite containing, on an elemental basis,about 0.01 to about 1 wt. percent platinum group metal, about 0.01 toabout 1 wt. percent rhenium, about 0.01 to about 5 wt. percent tin,about 0.01 to about 5 wt. percent of the alkali metal or alkaline earthmetal.

Other objects and embodiments of the present invention include specificdetails regarding essential and preferred catalytic ingredients,preferred amounts of components in the composite, suitable methods ofcomposite, suitable dehydrogenatable hydrocarbons, operating conditionsfor use in the dehydrogenation process, and the like particulars. Theseare hereinafter given in the following detailed disoussion of each ofthese facets of the present invention.

Regarding the dehydrogenatable hydrocarbon that is subjected to themethod of the present invention, it can, in general, be an organiccompound having 2 to 30 carbon atoms per molecule and containing atleast 1 pair of adjacent carbon atoms having hydrogen attached thereto.That is to say, it is intended to include the scope of the presentinvention, the dehydrogenation of any organic compound capable of beingdehydrogenated to produce products containing the same number of carbonatoms but fewer hydrogen atoms, and capable of being vaporized at thedehydrogenation temperatures --used herein. More particularly, suitabledehydrogenatable hydrocarbon area: aliphatic compounds containing 2 to30 carbon atoms per molecule, alkylaromatic hydrocarbons where we alkylgroup contains 2 to 6 carbon atoms, and naphthenes or alkyl-substitutednaphthenes. Specific examples of suitable dehydrogenatable hydrocarbonsare: (1) alkanes such as ethanes, propane, n-butane, isobutanes,n-pentane, isopentanes, n-hexane, 2-methylhexane and the like compounds;(2) naphthenes such as cyclopentane, cyclohexane, methylcyclopentane,1,3-dimethylcyclohexane and the like compounds; and, (3) alkylaromaticssuch as ethylbenzene, n-butylbenzene, 1,3,5-triethylbenzene,isopropylbenzene, ethylnaphthalene, and the like compounds.

In a preferred embodiment, the dehydrogenatable hydrocarbon having about4 to about 30 carbon atoms per molecule. For example, normal paraffinhydrocarbons containing about 10 to 15 carbon atoms per molecule aredehydrogenated by the subject method to produce the corresponding normalmono-olefin which can in turn, be alkylated with benzene and sulfonatedto make alkylbenzene sulfonate detergents having superiorbiodegradability. Likewise, n-alkanes having 12 to 18 carbons atoms canbe dehydrogenated to the corresponding normal mono-olefin which, inturn, can be sulfated or sulfonated to make excellent detergents.Similarly, n-alkane having 6 to 10 carbon atoms can be dehydrogenated toform the corresponding mono-olefin which can, in turn, by hydrated toproduce valuable alcohols. Preferred feed streams for the manufacture ofdetergent intermediate contains a mixture of 4 to 5 adjacent normalparaifin homologues such as C to C C to C C to C and the like mixtures.

An essential feature of the present invention involves the use of acatalytic composite comprising a combination of catalytically effectiveamounts of a platinum group component, a rhenium component, and a tincomponent with a porous carrier material. In a preferred embodiment,this catalytic composite also contains an alkali or alkaline earthcomponent.

Considering first the porous carrier material utilized in the presentinvention, it is preferred that the material be a porous, adsorptive,high-surface area support having a surface of about 25 to about 500 m./gm. The porous carrier material should be relatively refractory to theconditions utilized in the hydrocarbon conversion process,

and it is intended to include Within the scope of the present inventioncarrier materials which have traditionally been utilized indual-function hydrocarbon conversion catalysts such as: 1) activatedcarbon, coke, or charcoal; (2) silica or silica gel, silicon carbide,clays, and silicates including those synthetically prepared andnaturally occurring, which may or may not be acid treated, for example,attapulgus clay, china clay, diatomaceous earth, fullers earth, kaolin,kieselguhr, etc.; (3) ceramics, porcelain, crushed fireback, bauxite;(4) refractory inorganic oxides such as alumina, titanium dioxide,zirconium dioxide, chromium oxide, zinc oxide, magnesia, thoria, boria,silica-alumina, silica magnesia, chromia-alumina, alumina-boria,silica-zirconia, etc.; (5) crystallne aluminosilicates such as naturallyoccurring or synthetically prepared mordenite and/or faujasite, eitherin the hydrogen form or in a form which has been treated withmultivalent cations; and, (-6) combination of elements from one or moreof these groups. The preferred porous carrier materials for use in thepresent invention are refractory inorganic oxides, with best resultsobtained with an alumina carrier material. Suitable alumina materialsare the crystalline aluminas known as the gamma-, eta-, andthetaalumina, with gammaor eta-alumina giving best results. Inadditional, in some embodiments the alumina carrier material may containminor proportions of other well known refractory inorganic oxides suchas silica, zirconia, magnesia, etc.; however, the preferred support issubstantially pure gammaor eta-alumina. Preferred carrier materials havean apparent bulk density of about 0.3 to about 0.7 gm./ cc. and surfacearea characteristics such that the average pore diameter is about 20 to3000 angstroms, the pore volume is about 0.1 to about 1 mL/gm. and thesurface area is about 100 to about 500 m. gm. In general, best resultsare typically obtained with a gammaalumina carrier material which isused in the form of spherical particles having: a relatively smalldiameter (i.e., typically about inch), an apparent bulk density of about0.5 gm./cc., a pore volume of about 0.4 ml./gm., and a surface area ofabout 175 m. gm.

The preferred alumina carrier material may be prepared in any suitablemanner and may be synthetically prepared or natural occurring. Whatevertype of alumina is employed it may be activated prior to use by one ormore treatments including drying, calcination, steaming, etc., and itmay be in a form known as activated alumina, activated alumina ofcommerce, porous alumina, alumina gel, etc. For example, the aluminacarrier may be prepared by adding a suitable alkaline reagent, such asammonium hydroxide to a salt of aluminum such as aluminum chloride,aluminum nitrate, etc., in an amount to form an aluminum hydroxide gelwhich upon drying and calcining is converted to alumina.

The alumina carrier may be formed in any desired shape such as spheres,pills, cakes, extrudates, powders, granules, etc., and utilized in anydesired size. For the purpose of the present invention a particularlypreferred form of alumina is the sphere; and alumina spheres may becontinuously manufactured by the well known oil drop method whichcomprises: forming an alumina hydrosol by any of the techniques taughtin the art and preferably by reacting aluminum metal with hydrochloricacid, combining the resulting hydrosol with a suitable gelling agent anddropping the resultant mixture into an oil bath maintained at elevatedtemperatures. The droplets of the mixture remain in the oil bath untilthey set and form hydrogel spheres. The spheres are then continuouslywithdrawn from the oil bath and typically subjected to specific agingtreatments in oil and an ammoniacal solution to further improve theirphysical characteristics. The resulting aged and gelled particles arethen. washed and dried at a relatively low temperature of about 300 F.to about 400 F. and subjected to a calcination procedure at atemperature of about 850 F. to about 1300 F. for a period of about 1 toabout 20 hours. It is also a good practice to subject the calcinedparticles to a high temperature steam treatment in order to remove asmuch as possible of undesired acidic component. This manufacturingprocedure effects conversion of the alumina hydrogel to thecorresponding crystalline gamma-alumina.

See the teachings of US. Pat. No. 2,620,314 for additional details.

One essential constituent of the catalyst used in the present inventionis a tin component. This component may be present as an elemental metalor as a chemical compound such as the oxide, sulfide, halide, etc., andmay be utilized in any amount which 'is catalytically effective.Preferably, the tin component is used in an amount sufiicient to resultin the final catalytic composite containing, on an elemental basis,about 0.01 to about 5 wt. percent tin, with best results typicallyobtained with about 0.1 to about 1 wt. percent tin.

This tin component may be incorporated in the catalytic composite in anysuitable manner such as by coprecipitation or cogellation with theporous carrier material, ion exchange with the carrier material orimpregnation of the carrier material at any stage in the preparation. Itis to be noted that it is intended to include within the scope of thepresent invention all conventional methods for incorporating a metalliccomponent in a catalytic composite, and the particular method ofincorporation used is not deemed to be an essential feature of thepresent invention. One preferred method of incorporating the tincomponent into the catalytic composite involves coprecipitating the tincomponent during the preparation of the preferred refractory oxidecarrier material. In the preferred case, this involves the addition ofsuitable soluble, decomposable tin compounds such as stannous or stannichalide to the alumina hydrosol, and then combining the hydrosol with asuitable gelling agent and dropping the resulting mixture into an oilbath, etc., as explained in detail hereinbefore. Following thecalcination step, there is obtained a carrier material comprising anintimate combination of alumina and stannic oxide. Another preferredmethod of incorporating the tin component into the catalyst compositeinvolves the utilization of a soluble, decomposable compound of tin toimpregnate the porous carrier material, Thus, the tin component may beadded to the carrier material by commingling the latter with an aqueoussolution of a suitable tin salt or water-soluble compound of tin such asstannous bromide, stannic chloride, stannic chloride pentahydrate,stannic chloride tetrahydrate, stannic chloride trihydrate, stannicchloride diamino, stannic trichloride bromide, stannic chromate,stannous fluoride, stannic fluoride, stannic iodide, stannic sulfate,stannic tartrate, and the like compounds. The utilization of a tinchloride compound such as stannous or stannic chloride is particularlypreferred. In general, the tin component can be impregnated either priorto, simultaneously with, or after the other metallic components areadded to the carrier material. However, I have found that excellentresults are obtained when the tin component is impregnatedsimultaneously with the platinum and rhenium components. In fact, apreferred impregnation solution contains chloroplatinic acid, perrhenicacid, nitric acid, and stannous or stannic chloride.

Another essential ingredient of the catalytic composite used in thepresent invention is a platinum group component. Although the process ofthe present invention is specifically directed to the use of a catalyticcomposite containing platinum, it is intended to include other platinumgroup metals, such as palladium, rhodium, ruthenium, osmium, andiridium. The platinum group component such as platinum may exist withinthe final catalytic composite as a compound such as an oxide, sulfide,halide, etc., or as an element metal. Generally, the amount of theplatinum group component present in the final catalyst is small comparedto the quantities of the other components combined therewith. In fact,the platinum group component generally comprises about 0.01 to about 1%by weight of the final catalytic composite calculated on an elementalbasis. Excellent results are obtained when the catalyst contains about0.1 to about 0.9 wt. percent of the platinum group metal. The preferredplatinum group component is platinum or a compound of platinum.

The platinum group component may be incorporated in the catalyticcomposite in any suitable manner such as coprecipitation or cogellationwith the preferred alumina carrier material, ion exchange with thealumina carrier material and/or alumina hydrogel, or impregnation eitherafter or before calcination of the alumina hydrogel, etc. The preferredmethod of preparing the catalyst involves the utilization of a soluble,decomposable compound of the platinum group metal to impregnate theporous carrier material. Thus, the platinum group metal may be added tothe carrier by commingling the latter with an aqueous solution ofchloroplatinic acid. Other water-soluble compounds of platinum may beemployed as impregnation solutions and include ammonium chloroplatinate,platinum chloride, dinitrodiaminoplatinum, etc. The utilization of aplatinum chloride compound such as chloroplatinic acid is ordinarilypreferred. In addition, it

is generally preferred to impregnate the carrier material after it hasbeen calcined in order to minimize the risk of washing away the valuableplatinum metal compounds; however, in some cases it may be advantageousto impregnate the carrier when it is in a gelled state.

Yet another essential ingredient of the catalyst used in the presentinvention is the rhenium component. This component may be present as anelemental metal, as a chemical compound such as the oxide, sulfidehalide, etc., or as a physical or chemical combination with the porouscarrier material and/or other components of the catalytic composite. Therhenium component is preferably utilized in an amount sufiicient toresult in a final catalytic composite containing about 0.01 to about 1wt. percent rhenium, calculated on an elemental basis.

The rhenium component may be incorporated in the catalytic composite inany suitable manner and at any stage in the preparation of the catalyst.It is generally advisable to incorporate the rhenium component in animpregnation step after the porous carrier material has been formed inorder that the expensive metal will not be lost due to Washing andpurification treatments which may be applied to the carrier materialduring the course of its production. Although any suitable method for incorporating a catalytic component in a porous carrier material can beutilized to incorporate the rhenium component, the preferred procedureinvolves impregnation of the porous carrier material. The impregnationsolution can, in general, be a solution of a suitable soluble,decomposable rhenium salt such as ammonium perrhenate, so.- diumperrhenate, potassium perrhenate, and the like salts. In addition,solutions of rhenium halides such as rhenium chloride may be used; thepreferred impregnation solution is, however, an aqueous solution ofperrhenic acid. The porous carrier material can be impregnated with therhenium component either prior to, simultaneously with, or after theother components mentioned herein are combined therewith. Best resultsare ordinarily achieved when the rhenium component is impregnatedsimultaneously With the platinum group component. In fact, excellentresults have been obtained with a one-step impregnation procedureutilizing as an impregnation solution, an aqueous solution ofchloroplatinic acid, perrhenic acid, stannic chloride, and nitric acid.

Regarding the preferred amounts of the various metallic components ofthe subject catalyst, I have found it to be a good practice to specifythe amounts of the rhenium component and of the tin component as afunction of the amount of the platinum group component. On this basis,the amount of the rhenium component is ordinarily selected so that theatomic ratio of the platinum group metal to rhenium contained in thecomposite is about 0.05:1 to about 2.75:1, with the preferred rangebeing about 0.25:1 to about 2: 1. Similarly, the amount of the tincomponent is ordinarily selected to produce a composite containing anatomic ratio of the platinum group metal to tin of about 0.111 to about3:1 with the preferred range being about 0.5:1 to about 1.5:1.

Another significant parameter for the subject catalyst is the totalmetals content which is defined to be the sum of the platinum groupcomponent, the rhenium component, and the tin component, calculated onan elemental tin, rhenium, and platinum group metal basis. Good resultsare ordinarily obtained with the subject catalyst when this parameter isfixed at a value of about 0.03 to about 3 wt. percent, with best resultsordinarily achieved at a metals loading of about 0.15 toabout 2 Wt.percent.

Integrating the above discussion of each ofthe essen-' tial componentsof the catalytic composite used in'the present invention, it is evidentthat a particularly preferred catalytic composite comprises acombination of a platinum component, a rhenium component, and a tincomponent with an alumina carrier material in amounts sufiicient toabout 1 Wt. percent platinum, about 0.01 to about 1 wt. percent rhenium,and about 0.01 to about 5 wt. percent tin. Accordingly, specificexamples of especially preferred catalytic composites are as follows:(1) a catalytic composite comprising a combination of .5 wt. percenttin, .5 Wt. percent rhenium, and .75 wt. percent platinum With analumina carrier material; (2) a catalytic composite comprising acombination of .1 wt. percent tin, .1 Wt. percent rhenium, and 0.1 wt.percent platinum with an alumina carrier material; (3) a catalyticcomposite comprising a combination of about .375 Wt. percent.

tin, .375 wt. percent rhenium, and .375 Wt. percent platinum with analumina carrier material; (4)- a catalytic composition comprising acombination of .12 wt. percent tin, .1 Wt. percent rhenium, and .2 wt.percent platinum with an alumina carrier material; (5) a catalyticcomposite comprising a combination of 0.25 Wt. percent tin, 0.25 Wt.percent platinum, 0.25 wt. percent rhenium with an alumina carriermaterial; and, (6) a catalytic composite comprising a combination of 0.2wt. percent tin, 0.2 wt. percent rhenium, and 0.2 Wt. percent platinumwith an alumina carrier material. The amounts of the components reportedin these examples are, of course, calculated on an elemental basis. I

As indicated above, a preferred embodiment of the present inventioninvolves use of a catalytic composite containing an alkali or alkalineearth component. More specifically, this component is selected from thegroup consisting of the compounds of the alkali metalscesium, rubidium,potassium, sodium, and lithiumand of the alkaline earth metals-calcium,strontium, barium, and magnesium. This component may exist Within thecatalytic composite as a relatively stable compound such as the oxide orsulfide or in combination with one or more of the other components-ofthe composite, or in combination with an alumina carrier material suchas in the form of a metal aluminate. Since, as is explained hereinafter,the composite containing the alkali or alkaline earth is always calcinedin an air atmosphere before use in the conversion of hydrocarbons, themost likely state this component exists in during use in dehydrogenationis the metallic oxide. Regardless of What precise form in which. itexists in the composite, the amount of this component utilized ispreferably selected to provide a composite containing about 0.01 toabout 5 wt. percent of the alkali or alkaline earth metal, and morepreferably about 0.05 to. about 2.5 Wt. percent. Best results areordinarily achieved when this component is a compound of lithium orpotassium.

This alkali or alkaline earth component may be combined with the porouscarrier material in any manner known to those skilled in the art such asby impregnation, coprecipitation, physical admixture, ion exchange, etc.However, the preferred procedure involves impregnation of the carriermaterial either before or after it is calcined and either before,during, or after the other components are added to the carrier material.Best results are ordinarily obtained when this component is added afterthe platinum, rhenium, and tin component because it serves to neutralizethe acid used in the preferred impregnation procedure for incorporationof these components. Typically, the impregnation of the carrier materialis performed by contacting same with a solution of a suitabledecomposable compound or salt of the desired alkali or alkaline earthmetal. Hence, suitable compounds include the halides, sulfates,nitrates, acetates, carbonates, phosphates, and the like compounds. Forexample, excellent results are obtained by impregnating the carriermaterial after the platinum group component, rhenium component, and tincomponent have been combined therewith with an aqueous solution oflithium nitrate or potassium nitrate.

Regardless of the details of how the components of the catalyst arecomposited with the alumina carrier material, the composite, after eachof the components is added thereto, generally will be dried at atemperature of about 200 F. to about 600 F. for a period of from about 2to 24 hours or more and finally calcined at a temperature of about 600F. to about 1100 F. in an air atmosphere for a period of about 0.5 to 10hours, preferably about 1 to about 5 hours in order to substantiallyconvert the metallic components to the oxide form. When acidiccomponents are present in any of the reagents used to effectincorporation of any one of the components of the subject composite, itis a good practice to subject the resulting composite to a hightemperature treatment with steam, either after or before the calcinationstep described above, in order to remove as much as possible of theundesired acidic component. For example, when the platinum groupcomponent is incorporated by impregnating the carrier material withchloroplatinic acid, it is preferred to subject the resulting compositeto a high temperature treatment with steam in order to remove as much aspossible of the undesired chloride.

It is preferred tht the resultant calcined catalytic composite besubjected to a substantially water-free reduction prior to its use inthe conversion of hydrocarbons. This step is designed to insure auniform and finely divided dispersion of the metallic componentsthroughout the carrier material. Preferably, substantially pure and dryhydrogen (i.e., less than 20 vol. p.p.m. H is used as the reducing agentin this step. The reducing agent is contacted with the calcinedcomposite at a temperature of about 800 F. to about 1200 F. and for aperiod of time of about 0.5 to hours or more, effective to substantiallyreduce the metallic components to their elemental state. This reductiontreatment may be performed in situ as part of a start-up sequence ifprecautions are taken to predry the plant to a substantially water-freestate and if substantially water-free hydrogen is used.

Although it is not essential, the resulting reduced catalytic compositemay, in some cases, be beneficially subjected to a presulfidingoperation designed to incorporate in the catalytic composite from about0.05 to about 0.5 wt. percent sulfur calculated on an elemental basis.Preferably, this presulfiding treatment takes place in the presence ofhydrogen and a suitable sulfur-containing compound such as hydrogensulfide, lo-wer molecular weight mercaptans, organic sulfides, etc.Typically, this procedure comprises treating the reduced catalyst with asulfiding gas such as a mixture containing a mole ratio of H to H 8 ofabout 10:1 at conditions sufficient to effect the desired incorporationof sulfur, generally including a temperature ranging from about 50 F. upto about 1-,100 F. or more. This presulfiding step can be performed insitu or ex situ.

F. or more. This presulfiding step can be performed in situ or ex situ.

According to the method of the present invention, the dehydrogenatablehydrocarbon is contacted with a catalytic composite of the typedescribed above in a dehydrogenation zone at dehydrogenation conditions.This contacting may be accomplished by using the catalyst in a fixed bedsystem, a moving bed system, a fluidized bed system, or in a batch typeoperation; however, in view of the danger of attrition losses of thevaluable catalyst and of well known operational advantages, it ispreferred to use a fixed bed system. In this system, the hydrocarbonfeed stream is preheated by any suitable heating means to the desiredreaction temperature and then passed into a dehydrogenation zonecontaining a fixed bed of the catalyst type previously characterized. Itis, of course, understood that the dehydrogenation zone may be one ormore separate reactors with suitable heating means therebetween toinsure that the desired conversion temperature is maintained at theentrance to each reactor. It is also to be noted that the reactants maybe contacted with the catalyst bed in either upward, downward, or radialflow fashion with the latter being preferred. In addition, it is to benoted tht the reactants may be in the liquid phase, a mixed liquid-vaporphase, or a vapor phase when they contact the catalyst, 'with bestresults obtained in the vapor phase.

-Although hydrogen is the preferred diluent for use in the subjectdehydrogenation method, in some cases other art-recognized diluents maybe advantageously utilized such as steam, methane, carbon dioxide, andthe like diluent. Hydrogen is preferred because it serves thedualfunction of not only lowering the partial pressure of thedehydrogenatable hydrocarbon, but also of suppressing the formation ofhydrogen-deficient, carbonaceous deposits on the catalytic composite.Ordinarily, hydrogen is utilized in amounts sufficient to insure ahydrogen to hydrocarbon mole ratio of about 1:1 to about 20: l, withbest results obtained in the range of about 1.5:1 to about 10:1. Thehydrogen stream charged to the dehydrogenation zone will typically berecycle hydrogen obtained from this zone after a suitable separationstep.

Regarding the conditions utilized in the process of the presentinvention, these are generally selected from the conditions well knownto those skilled in the art for the particular dehydrogenatablehydrocarbon which is charged to the process. More specifically, suitableconversion temperatures are selected from the range of about 700 toabout 1250 F., with a value being selected from the lower portion ofthis range for the more easily dehydrogenated hydrocarbons such as thelong chain normal parafiins and from the higher portion of this rangefor the more difiiculty dehydrogenated hydrocarbons such as propane,butane, and the like hydrocarbons. For example, for the dehydrogenationof C to C normal paraffiris, best results are ordinarily obtained at atemperature of about 800 to about 950 F. The pressure utilized isordinarily selected at a value which is as low as possible consistentwith the maintenance of catalyst stability and is usually about 0.1 toabout 10 atmospheres, with best results ordinarily obtained in the rangeof about .5 to about 3 atmospheres. In addition, a liquid hourly spacevelocity (calculated on the basis of the vacuum amount, as a liquid, ofhydrocarbon charged to the dehydrogenation zone per hour divided by thevolume of the catalyst bed utilized) is selected from the range of about1 to about 40 hrf with best results for the dehydrogenation of longchain normal paraffins typically obtained at relatively high spacevelocity of about 25 to 35 hrf Regardless of the details concerning theoperation of the dehydrogenation step, an efiluent stream will bewithdrawn therefrom. This effluent will contain unconverteddehydrogenatable hydrocarbons, hydrogen, and products of thedehydrogenation reaction. This stream is typically cooled and passed toa separating zone wherein a hydrogen-rich vapor phase is allowed toseparate from a hydrocarbon-rich liquid phase. In general, it is usuallydesired to recover the unreacted dehydrogenatable hydrocarbon from thishydrocarbon-rich liquid phase in order to make the dehydrogenationprocess economically attractive. This recovery step can be accomplishedin any suitable manner known to the art such as by passing thehydrocarbon-v rich liquid phase through a bed of suitable adsorbentmaterial which has the capacity to selectively retain the dehydrogenatedhydrocarbons contained therein or by contacting same with a solventhaving a high selectivity for the dehydrogenated hydrocarbon, or by asuitable fractionation scheme where feasible. In the case where thedehydrogenated hydrocarbon is a monoolefin, suitable adsorbents havingthis capacity are activated silica gel, activated carbon, activatedalumina, various types of specilly prepared molecular sieves, and thelike adsorbents. In another typical case, the dehydrogenatedhydrocarbons can be separated from the unconverted dehydrogenatablehydrocarbons by utilizing the inherent capability of the dehydrogenatedhydrocarbons to easily enter into several well known chemical reactionssuch as alkylation, oligomerization, halogenation, sulfonation,hydration, oxidation, and the like reactions. Irrespective of how thedehydrogenated hydrocarbons are separated from the unreactedhydrocarbons, a stream containing the unreacted dehydrogenatablehydrocarbons will typically be recovered from this hydrocarbonseparation step and recycled to the dehydrogenation step. Likewise, thehydrogen phase present in the hydrogen separating zone will be withdrawntherefrom, a portion of it vented from the system in order to remove thenet hydrogen make, and the remaining portion is typically recycledthrough suitable compressing means to the dehydrogenation in order toprovide diluent hydrogen therefor.

In a preferred embodiment of the present invention wherein long chainnormal parafiin hydrocarbons are dehydrogenated to the correspondingnormal monoolefins, a preferred mode of operation of this hydrocarbonrecovery step involves an alkylation reaction. In this mode, thehydrocarbon-rich liquid phase withdrawn from the separating zone iscombined with a stream containing an alkylatable aromatic and theresulting mixture passed to an alkylation zone containing a suitablehighly acid catalyst such as an anhydrous solution of hydrogen fluoride.In the alkylation zone the mono-olefins react with the alkylatablearomatic while the unconverted normal paraffins remain substantiallyunchanged. The effiuent stream from the alkylation zone can then beeasily separated, typically by means of a suitable fractionation system,to allow recovery of the unreacted normal paraflins. The resultingstream of unconverted normal paraflins is then usually recycled to thedehydrogenation step of the present invention.

The following working examples are introduced to illustrate further thenovelty, mode of operation, utility, and benefits associated with thedehydrogenation method of the present invention. These examples areintended to be illustrative rather than restrictive.

These examples are all performed in a laboratory scale dehydrogenationplant comprising a reactor, a hydrogen separating zone, a heating means,cooling means, pumping means, compressing means, and the like equipment.In this plant, the feed stream containing the dehydrogentablehydrocarbon is combined with a hydrogen stream and the resultant mixtureheated to the desired conversion temperature, which refers hereinto thetemperature maintained at the inlet to the reactor. The heated mixtureis then passed into contact with the catalyst which is maintained as afixed bed of catalyst particles in the reactor. The pressures reportedherein are recorded at the outlet from the reactor. An effluent streamis withdrawn from the reactor, cooled, and passed into the separatingzone wherein a hydrogen gas phase separates from a hydrocarbon-richliquid phase containing dehydrogenated hydrocarbons, unconverteddehydrogenatable hydrocarbons, and a minor amount of side products ofthe dehydrogenation reaction. A portion of the hydrogen-rich gas phaseis recovered as excess recycle gas with the remaining portion beingcontinuously recycled through suitable compressive means to the heatingzone as described above.

The hydrocarbon rich liquid phase from the separation zone is Withdrawntherefrom and subjected to analysis to determine conversion andselectivity for the desired dehydrogenated hydrocarbon as will beindicated in the examples. Conversion numbers of the dehydrogenatablehydrocarbon reported herein are all calculated on the basis ofdisappearance of the dehydrogenatable hydrocarbon and are expressed inmole percent. Similarly, selectivity numbers are reported on the basisof moles of desired hydrocarbon produced per 100 moles ofdehydrogenatable hydrocarbon converted.

All of the catalysts utilized in these examples are prepared accordingto the following general method with suitable modifications instoichiometry to achieve the compositions reported in each example.First, an alumina carrier material comprising inch spheres is preparedby: forming an aluminum hydroxyl chloride sol by dissolvingsubstantially pure aluminum pellets in a hydrochloric acid solution,adding hexamethylenetetramine to the sol, gelling the resulting solutionby dropping it into an oil bath to form spherical particles of analumina hydrogel, aging and washing the resulting particles with anammoniacal solution and finally drying, calcining, and steaming the agedand washed particles to form spherical particles of gamma-aluminacontaining substantially less than 0.1 wt. percent combined chloride.Additional details as to this method of preparing this alumina carriermaterial are given in the teachings of US. Pat. No. 2,620,314. Theresulting gamma-alumina particles are then contacted with animpregnation solution containing chloropla'tinic acid, perrhenic acid,stannic chloride, and nitric acid in amounts sufiicient to yield a finalcatalytic composite containing the desired amounts of platinum, rheniumand tin. The impregnated spheres are then dried at a temperature ofabout 300 F. for about an hour and thereafter calcined in an airatmosphere at a temperature of about 500 F. to about 1000 F. for about 2to 10 hours. In general, it is a good practice to thereafter treat theresulting calcined particles with an air stream containing about 10 toabout 30%, steam at a temperature of about 1000 F. for an additionalperiod of about 5 hours in order to further reduce the residual combinedchloride contained in the catalyst. In the cases shown in the 'examplewhere the catalyst utilized contains an alkali component, this componentis added to the oxidized platinum, rhenium, and tin-containing catalystin a separate impregnation step. This second impregnation step involvescontacting the oxidized particles with an aqueous solution of a suitabledecomposable salt of the alkali component. For the catalyst utilized inthe present examples, the salt is either lithium nitrate or potassiumnitrate. The amount of the salt of the alkali metal utilized is chosento result in a final catalyst of the desired composition. The resultingalkali impregnated particles are then dried and calcined in an airatmosphere in much the same manner as is described above following thefirst impregnation step.

In all of the examples the catalyst is reduced during start-up bycontacting with hydrogen at an elevated temperature and thereaftersulfided with a mixture of H and H 5.

EXAMPLE I The reactor is loaded with 100 cc. of a catalyst containing,on an elemental basis, 0.75 wt. percent platinum, 0.5 wt. percentrhenium, 0.5 wt. percent tin, and less than 0.15 wt. percent chloride.The feed stream utilized is commercial grade isobutane containing 99.7wt. percent isobutane and 0.3 wt. percent normal butane. The feed streamis contacted with the catalyst at a temperature of 1065 F., a pressureof 10 p.s.i.g., a liquid hourly space velocity of 4.0 hrf and a hydrogento hydrocarbon mole ratio of 2:1. The dehydrogenation plant is lined-outat these conditions and a 20 hour test period commenced. The hydrocarbonproduct stream from the plant is continuously analyzed by GLC(gas-liquid chromotography) and a high 13 conversion of isobutane isobserved with a selectivity for isobutylene of 80%.

EXAMPLE II The catalyst contains, on an elemental basis, 0.375 wt.percent platinum, 0.375 Wt. percent rhenium, 0.5 wt. percent tin, 0.6wt. percent lithium, and 0.15 wt. percent combined chloride. The feedstream is commercial grade normal dodecane. The dehydrogenation reactoris operated at a temperature of 870 F., a pressure of p.s.i.g., a liquidhourly space velocity of 32 hr.- and a hydrogen to hydrocarbon moleratio of 8: 1. After a line-out period a 20 hour test period isperformed during which the average conversion of the normal dodecane ismaintained at a high level with a selectivity for dodecene of about 90%.

EXAMPLE III The catalyst is the same as utilized in Example II. The feedstream is normal tetradodecane. The conditions utilized are atemperature of 840 F., a pressure of 20 p.s.i.g., a liquid hourly spacevelocity of 32 hrr and a hydrogen to hydrocarbon mole ratio of 8: 1.After a lineout period, a 20 hour test shows an average conversion ofabout 12.0%, and a selectivity for tetradodecene of 90%.

EXAMPLE IV The catalyst contains, on an elemental basis, 0.30 wt.percent platinum, 0.30 wt. percent rhenium, 1.0 wt. percent tin, and 0.6wt. percent lithium, with combined chloride being less than 0.2 wt.percent. The feed stream is substantially pure normal butane. Theconditions utilized are a temperature of 950 F., a pressure of p.s.i.g.,a liquid hourly space velocity of 4.0 hr.- and a hydrogen to hydrocarbonmole ratio of 4:1. After a line-out period, a hour test is performedwith the average conversion of the normal butane being about and theselectivity for butene is about 80%.

EXAMPLE V The catalyst contains, on an elemental basis, 0.75 wt. percentplatinum, 0.5 wt. percent rhenium, 1.0 wt. percent tin, 1.5 wt. percentpotassium, and less than 0.2 wt. percent combined chloride. The feedstream is commercial grade ethylbenzene. The conditions utilized are apressure of 15 p.s.i.g., a liquid hourly space velocity of 32 hI'. atemperature of 1050 F., and a hydrogen to hydrocarbon mole ratio of 8:1.During a 20 hour test period, 85% of equilibrium conversion of theethylbenzene is observed. The selectivity for styrene is 98.0%

I claim as my invention:

1. A method for dehydrogenating a dehydrogenatable hydrocarboncomprising contacting said hydrocarbon at dehydrogenation conditionswith a catalytic composite comprising a combination of a platinum groupcomponent, a rhenium component and a tin component with a porous carriermaterial in amounts sufiicient to result in a composite containing, onan elemental basis, about 0.01 to about 1 wt. percent of the platinumgroup metal, about 0.01 to about 1 wt. percent rhenium and about 0.01 toabout 5 wt. percent tin.

2. A method as defined in claim 1 wherein said dehydrogenatablehydrocarbon is admixed with hydrogen when it contacts said catalyticcomposite.

3. A method as defined in claim 1 wherein said platinum group componentof the composite is platinum or a compound of platinum.

4. A method as defined in claim 1 wherein said porous carrier materialis a refractory inorganic oxide.

5. A method as defined in claim 4 wherein said refractory inorganicoxide is alumina.

6. A method as defined in claim 1 wherein said dehydrogenatablehydrocarbon is an aliphatic compound containing 2 to 30 carbon atoms permolecule.

7. A method as defined in claim 1 wherein said dehydrogenatablehydrocarbon is a normal parafiin hydrocarbon containing 4 to 30 carbonatoms per molecule.

8. A method as defined in claim 1 wherein said de hydrogenatablehydrocarbon is a naphthene.

9. A method as defined in claim 2 wherein said dehydrogenatableconditions include a temperature of about 700 to about 1250 F., apressure of about 0.1 to about 10 atmospheres, an LHSV of about 1 toabout 40 hIS. and a hydrogen to hydrocarbon mole ratio of about 1:1 toabout 20: 1.

10. A method for dehydrogenating a dehydrogenatable hydrocarboncomprising contacting the hydrocarbon at dehydrogenation conditions witha catalytic composite comprising a combination of a platinum groupcomponent, a rhenium component, a tin component and an alkali oralkaline earth component with a porous carrier material in amountssufficient to result in a composite containing, on an elemental basis,about 0.01 to about 1 wt. percent platinum group metal, about 0.01 toabout 1 wt. percent rhenium, about 0.01 to about 5 wt. percent tin andabout 0.01 to about 5 wt. percent of the alkali metal or alkaline earthmetal.

11. A method as defined in claim 10 wherein the platinum group componentof the composite is platinum or a compound of platinum.

12. A method as defined in claim 10 wherein said porous carrier materialis a refractory inorganic oxide.

13. A method as defined in claim 12 wherein said refractory inorganicoxide is alumina.

14. A method as defined in claim 10 wherein the alkali or alkaline earthcomponent of the composite is a compound of lithium.

15. A method as defined in claim 10 wherein the alkali or alkaline earthcomponent of the composite is a compound of potassium.

16. A method as defined in claim 10 wherein said dehydrogenatablehydrocarbon is admixed with hydrogen when it contacts the catalyticcomposite.

17. A method as defined in claim 10 wherein said dehydrogenatablehydrocarbon is an aliphatic compound containing 2 to 30 carbon atoms permolecule.

18. A method as defined in claim 10 wherein said dehydrogenatablehydrocarbon is a normal parafiin hydrocarbon containing about 4 to about30 carbon atoms per molecule.

19. A method as defined in claim 10 wherein said dehydrogenatablehydrocarbon is a normal paraffin hydrocarbon containing about 10 toabout 15 carbon atoms per molecule.

20. A method as defined in claim 10 wherein said dehydrogenatablehydrocarbon is an alkyl-aromatic, the alkyl group of which contains 2 to6 carbon atoms.

21. A method as defined in claim 10 wherein said dehydrogenatablehydrocarbon is a naphthene.

References Cited UNITED STATES PATENTS 3,326,961 6/1967 Eden et al.3,389,965 6/1968 Ruiter et al. 3,449,078 6/ 1969 Quik et al. 3,449,2376/ 1969 Jacobson et al.

CURTIS R. DAVIS, Primary Examiner US. Cl. X.R. 260668, 683.3

